Measuring and control apparatus



0 :00 ADJ-OE m0 ZOFPOWJuuO ATNEY wczoouw O a .P

INVENTOR.

HARRY S. JONES BY I FDAPDO muiom 2:2-

0: MOE

H S JONES MEASURING AND CONTROL APPARATUS Filed June 12, 1942 June 20,1944.

Patented June 20, 1944 I 2,352,103 MEASURING AND CONTROL APPARATUS HarryS. Jones, Washington, D. C., assignor to The Brown Instrument Company,Philadelphia, Pa., a corporation of Pennsylvania Application June 12,1942, Serial No. 446,828

22 Claims.

The present invention relates to automatic electrical systems formeasuring and/or controlling the magnitude or changes in magnitude of avariable condition, and more particularly, to such systems wherein adelicate and extremely sensitive measuring instrument, for example, agalvanometer, is arranged to control the operation of relatively heavyindicating or recording struc--' ture, or control mechanism such as arheostat or valve. The invention has particular utility in high speedpyrometric recording and controlling systems wherein it is desired torecord and control the temperature at one or more remote points, forexample, in furnaces or kilns.

In high speed recording and/or controlling apparatus known in the priorart 'considerable difficulty has been experienced due to undesirableeffects produced upon the operation of the apparatus by vibration andshock to which the apparatus is subjected under normal conditions ofuse. One particularly undesirable effect of vibration and shock uponsuch prior art apparatus is that the apparatus is rendered erratic andunstable in operation. By means of the present invention the effects ofvibration and shock upon the operation of such apparatus has beenreduced to a minimum.

A general object of the present invention is to provide simple andefficient means for neutralizing the effects of vibration and shock uponthe operation of systems of the type referred to above. A more specificobject of the invention is to provide a supporting structure for thegalvanometer which absorbs to a considerable extent the vibration andshock to which apparatus of the type referred to above is subjectedunder normal conditions of use whereby the effects of vibration andshock upon the operation of the apparatus are substantially reduced.

Another specific object of the invention is to provide means fordelaying the response of such apparatus to transient deflections of thegalvanometer which may be produced by vibration and shock to therebyminimize the effects of vibration and shock upon the operation of theapparatus.

A further specific object of the invention is to provide a supportingstructure for the galvanometer which absorbs the vibration and shock towhich such apparatus is subjected, and in addition to provide means fordelaying the response of the apparatus to transient galvanometerdefiections whereby the effects of vibration and shock upon theoperation of the apparatus are reduced to a minimum.

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,however, and the advantages possessed by it reference should be had tothe accompanying drawing and descriptive matter in which I haveillustrated and described a preferred embodiment of the invention.

Of the drawing:

Fig. 1 is a diagrammatic illustration of the use of the invention in aself balancing potentiometric network;

Figs. 2-4 illustrate in detail a portion of the supporting structure forthe galvanometer in the Fig. 1 arrangement; and

Fig. 5 shows curves illustrating the operation of the arrangement ofFig. 1.

In Fig. 1 of the drawing an arrangement including an electronic device Ito be described is illustrated for producing effects in accordance withthe extent of unbalance of a potentiometric network which controls theelectronic device and is unbalanced in accordance with the variations ina. quantity to be measured and in which because of the small magnitudeof the unbalanced electromotive forces produced in the network it is notpractical, nor desirable, to have the said effects directly produced bythe potentiometric network.

Specifically, an arrangement is illustrated in Fig. 1 for measuring andrecording the temperature of a furnace 2 in the interior of which athermocouple 3 is inserted and is responsive to slight changes in thetemperature therein. The terminals of the thermocouple 3 are connectedby conductors 4 and 5 to the terminals of a null point potentiometricnetwork 6 which may be of any suitable type such as the Brownpotentiometric network disclosed in the Harrison et a1. Patent 2,150,502issued March 14, 1939.

The movable coil 1 of a sensitive galvanometer 8 is connected in theconductor 5 by means including the galvanometer suspension means to bedescribed hereinafter. A pick-up coil 9 which is positioned in analternating magnetic field and is supported by the same suspension whichsupports the movable coil I of the galvanometer 8 is adapted to bedeflected in correspondence with the deflections of the movable coil 1.This pickup coil 9 is positioned between the poles of a suitable fieldstructure N on which is wound a field winding II which is energized fromalternating current supply conductors L and U and is so arranged withrespect to the field structure III that when the galvanometer movablecoil I is in its undefiected position the pick-up coil I is in zeroinductive relation to the alternating magnetic field set up in the fieldstructure ll. When the galvanometer movable coil 1 deflects in onedirection or the other the pick-up coil 9 deflects accordingly and as aresult an alternating voltage in phase with or 180' out of phase withthe line voltage is induced in the pick-up coil I.

The potentiometric network l is of a well known type and it is sumcientfor the present purposes to point out that the potentiometric networkincludes a circuit branch including the thermocouple I and an opposingcircuit branch including a source of known potential such as a batteryI2, resistances ll, a variable portion of which may be connected intothe opposed branches by means of sliding contact l4 whereby therespective effects of the variable and known sources are made equal andopposite and the galvanometer movable coil I is then renderedundeflected when the circuit is balanced for a given value of the E. M.F. of the thermocouple 2 with contact H in a corresponding positionalong resistances IS. The position of the contact I 4 along theresistances II is then a measure of the value of the electromotive forceproduced by the thermocouple 3 and may serve as a measure of thetemperature to which the thermocouple is exposed.

In this embodiment of my invention the means by which the contact [4 isadjusted back and forth along resistances ll in response to galvanometerdeflection includes a reversible rotating field motor I! which isadapted to be selectively energized for rotation in one direction or theother from the electronic amplifier I. When the electromotive forceproduced by the thermocouple changes in response to a change intemperature within the furnace 2 the galvanometer movable coil I will bedeflected in one direction or the other and consequently the pickup coil9 will be rotated into inductive relation with the alternating magneticfield set up in the field structure l resulting in the induction of analternating voltage in the pick-up coil 8. The phase and amplitude ofthe alternating voltage so induced in the pick-up coil 9 is determinedby the direction and extent of deflection of the latter from itsposition of zero inductive relation in the magnetic field. This inducedalternating voltage is connected by means of the galvanometer suspensionmeans to be described and conductors i8 and II to the input circuit ofthe electronic amplifier I so that depending upon the direction ofdeflection of the movable coil I of the galvanometer I the motor l willbe energized for rotation in one direction or the other to effect anadjustment of the sliding contact l4 along the resistances ii torebalance the potentiometric network 6.

The shaft of the motor I5 is connected in any convenient manner to ascrew threaded shaft II, and the potentiometer contact I4 is mounted ona carriage is which is carried by the shaft II and is adapted to bemoved in one direction or the other as a shaft I! is rotated. Thus, whenthe motor I! is energized for rotation as a result of change inthermocouple electromotive force the motor will effect movement of thecontact 14 along the resistances l3 in the roper direction until thepotentiometric network 5 is again balanced. The galvanometer deflectionwill then be reduced to zero and the motor will come to rest with thecontact i 4 at a new position along the resistances i3, which positionwill then be a measure of the temperature of the interior of the furnaceI.

If desired, a pen 20 may be mounted on the carriage which carriespotentiometer contact I4 and arranged in cooperative relation with arecorder chart 2| to thereby provide a continuous record of thetemperature of the interior of the furnace I. The chart 2| may be astrip chart as shown and is adapted to be driven in any convenientmanner 9.5,.101 example, by a unidirectional electrical motor 22'through suitable gearing (not shown) V so that the record of thetemperature to which the thermocouple 3 is sub- Jected will be recordedas a continuous line on the chart.

The electronic amplifier I referred to includes an electronic valve 22to the input circuit of which the voltage induced in the pick-up coil Iis applied. Valve 22 is a heater type pentode and includes an anode 23,a suppressor grid 24. a screen grid 25, a control grid 26, a cathode 21and a filament 28. The filament 28 is connected by conductors not shownin order not to confuse the drawing to the low voltage secondary winding29 of a transformer 30 having a line voltage primary winding 3|, a highvoltage secondary winding 32, and low voltage secondary windings 33 and34 in addition to the low voltage secondary winding 29. The low voltagesecondary winding 29 is also connected to and supplies energizingcurrent to the heater filaments I5, 38 and 31 of electronic valves 38,39 and 40, respectively.

An electronic valve 4! is also utilized, which valve may be aconventional full wave rectifier, and is employed to provide a source ofdirect current voltage for energizing the output circuit of the valves22, 3B, 39 and 40. Valve 4| includes a filament cathode 42 and anodes 43and 44. The filament cathode 42 of valve 4| is connected to the lowvoltage transformer sec-,

ondary winding 33 and receives energizing current therefrom. The anodes43 and 44 are connected by conductors 45 and 46 with the terminals ofthe high voltage secondary winding 22, and the rectified current isconnected across the input terminals of a suitable filter 41. A centerta on the secondary winding 32 is connected by a grounded conductor 48to one input terminal of the filter 41 which is indicated by dottedlines and the other input terminal of the filter is connected to thefilament cathode 42 so that a direct current voltage is maintainedacross the filter. The output terminals of the filter 41 are connectedto the output circuits of the electronic valves 22, 38, 39 and 40, andtherefore, due to the filtering action of the filter a direct currentvoltage substantially free from alternating components is applied to theanode circuits of the valves 22, 3B, 39 and 40.

The output circuit of valve 22 may be traced from a positive terminal 49of the filter 41 through a resistance 50 to anode 23, cathode 21, abiasing resistance 5| "which is shunted by a condenser 52 and aconductor 53 to the grounded and negative terminal of the filter 41. Thesuppressor grid 24 of valve 22 is directly connected to the cathode 21and the screen grid 25 is connected by a conductor 54 to the positiveterminal 55 of the filter 41.

The voltage induced in the pick-up coil 8 is impressed by the conductorsl6 and II between the control grid 26 and cathode 21 of valve 22 throughthe biasing resistance 8|, and the output circuit of the valve 22 isresistance capacity coupled to the input circuit of the electronic valve38 which, as shown, is also a heater type pentode. The electronic valves22 and 38 may desirably be of the type known commercially as the 6J7.

Valve 38 includes an anode 58, a suppressor grid 51, a screen grid 58, acontrol grid 58 and a cathode 88 in addition to the filament 35. Thesuppressor grid 51 is directly connected to the cathode 88 and thescreen grid 58 is connected by conductor 54 to the positive termina1 55of the filter 41. The control grid 59 is connected through a condenser8| to the anode 23 of valve 22 and is also connected through aresistance 82 and a biasing resistance 83 which is shunted by acondenser 84 to the cathode 88. The output circuit of valve 38 may betraced fromthe positive terminal 85 of the filter 41 through the primarywinding 88 of a transformer 81 having a center tapped secondary winding88 to the anode 58, cathode 88, the biasing resistance 83 and condenser84 to the conductor 53 and thereby to the negative terminal of thefilter.

The output circuit of valve 38 is coupled by the transformer 81 to theinput circuits of the valves 39 and 48. The valves 39 and 48 are heatertype tetrodes, and may desirably be type 6L6s. As illustrated, thevalves 39 and 48 are connected in push-pull. In addition to the filament38, valve 39 includes an anode 89, a screen grid 18, a control grid 1|and a cathode 12, and in addition to the filament 31 valve 48 includesan anode 13, a screen grid 14, a control grid 15, and a cathode 18. Oneterminal of the transformer secondary winding 88 is connected to thecontrol grid 1|, the other terminal is connected to the control grid 15,and the cathodes 12 and 18 are connected by a resistance 11, and aresistance 18 which is shunted by a condenser 19 to the center tap onthe winding 88. The resistance 18, which may desirably comprise thefilament of a lamp 88, and the condenser 19 provide a bias voltage forthe input circuits of valves 39 and 48 and are utilized for a purposeexplained in detail hereinafter.

The anodes 89 and 13 are connected to opposite terminals of the primarywinding 8| of a transformer 82 by conductors 83 and 84, respectively. Acenter tap on the primary winding 8| is connected by a conductor 85 tothe positive terminal 88 of the filter 41, and the negative terminal ofthe filter 41, which terminal as noted above is grounded, is connectedto the negative end of the resistance 11 and therethrough to thecathodes 12 and 18. The transformer 82 is also provided with twosecondary windings 81 and 88.

As shown, the screen grids 18 and 14 are connected together and areconnected through a resistance 89 to the positive terminal 88 of thefilter 41.

In operation when an alternating voltage is applied to the input circuitof the valve 22 by the pick-up coil 9, the valve 22 is alternatelyrendered more conductive and less conductive at the frequency of thevoltage of the supply lines L and L and consequently, a pulsatingpotential drop is produced across the resistance 58 in the anode circuitof valve 22. This pulsating potential drop will be in phase with thesupply line voltage or displaced 180 in phase therefrom depending uponthe direction of deflection of the pick-up coil 9 from its position ofzero inductive relation in the field structure l8 and the magnitudethereof will vary in accordance with the extent of deflection of thepick-up coil 8 from that position. The pulsating voltage so derived isapplied by means of the condenser 8| and resistance 82 to the inputcircuit of valve 38. The valve 38 is thus alternately rendered moreconductive and less conductive at the supply line frequency, andaccordingly, a pulsating current flows through the transformer primarywinding 88, which pulsating current will vary in phase and magnitude inaccordance with the phase and magnitude of the pulsating potential dropproduced across the resistance 58. This pulsating current flow throughthe transformer primary winding 88 causes the induction of analternating voltage in the secondary winding 88 which will vary in phaseand magnitude in accordance with the phase and magnitude of thepulsating current in the primary winding 88.

When an alternating voltage is thus produced across the terminals of thesecondary winding 88, the potentials of the control grids 1| and 15 areswung in opposite phase at a frequency corresponding to the supply linefrequency, and the valves 38 and 48 are alternately rendered conductiveand non-conductive, one valve being conductive while the other isnon-conductive. The resulting pulsating current flows through thetransformer primary winding 8| in successively opposite directionsthrough the opposite halves of the transformer resultin the induction ofan alternating voltage of line frequency in the transformer secondarywindings 81 and 88 whose phase and amplitude is determined by thedirection and extent of deflection of the pick-up coil 9 from its normalposition of zero inductive relation in the field structure I8.

The terminals of the transformer secondary winding 81 are connected toone phase winding 89 of the two-phase rotating field motor l5 byconductors 98 and 9|, and the other phase winding 92 of the motor isconnected to the supply lines L and L through a suitable condenser 93.Due to the action of the condenser 93 the current flow through the motorwinding 92 will lead the line current by approximately and since themotor winding 89 is arranged to be energized by currents in phase withor 180 out of phase with the line current, the magnetic fields set up bythese windings will be displaced by approximately 90 in space with theresult that a rotating magnetic field will be set up in the motor |5 inone direction or the other and the motor rotor will accordingly berotated in a corresponding direction. Thus, depending upon the directionof deflection of the pick-up coil 9 and thereby upon the direction ofunbalance of the potentiometric network 1, the motor |5 will beselectively energized for rotation in one direction or the other, and itwill be apparent the motor speed will be directly dependent upon themagnitude of the potentiometric unbalance current flow.

As illustrated, condensers 94 and 95 are connected across thetransformer windings 88 and BI, respectively. Due to the action ofcondenser 94 a full wave electromotive force is impressed on the controlgrids 1| and 15 from the half wave impulses impressed upon thtransformer primary winding 88 through the half wave rectifying actionof the valve 38. The condenser 95 tunes to resonance the transformer 82and its load consisting of the motor windings so that the current fiowsthrough the motor winding 89 will be at a maximum value for anyunbalance of the potentiometric network 8.

In order that the speed of motor |5 may be as great as possible duringrebalancing o! the potentiometric network without overshooting of thebalance point and consequent hunting taking place, means have beenprovided to ensure that the motor speed and the rate of change of itsspeed is substantially proportional to the extent of unbalance. Thisresult is obtained by introducing into the network in series with thealternating voltage derived from the pick-up coil 0 a voltage whosemagnitude is a function of the motor speed. Thus. as the slidewirecontact II approaches its new balance position, the deflection of thepick-up coil 0 will decrease and accordingly, the alternating voltagederived from the latter will decrease in value and if the mo-- tor speedis then such that it would ordinarily coast beyond the balance positiondue to its inertia, the opposing voltage which is introduced in circuitwill be appreciably greater than the unbalance voltage and will tend toeffect energization of the motor in the opposite direction and therebyproduce a positive damping action which will check the motor speedbefore balance is reached and gradually reduce it to zero as thepotentiometric unbalance is reduced to zero.

Specifically, a pair of opposed windings 00 and 01 of an induction discgenerator 98 are connected in series in the input circuit of the valve22 in series with the pick-up coil 0, and the windings l0 and 01 are soarranged that the generated voltage will be opposed to the voltageproduced in the pick-up coil 0. A variable resistor 00 is connectedacross the generator coils 08 and 01 and is provided for permittingadjustment of the magnitude of the voltage opposed to the voltage ofpick-up coil 0 to be readily made.

The induction disc generator 08 comprises a rotatable aluminum or copperdisc I00 which may be driven directly from the shaft of motor I! orthrough suitable gearing, as desired, and also includes a winding IOIwhich is connected by conductors not shown to the transformer secondarywinding 04 and receives energizing current therefrom. The winding IOI isarranged on one side of the disc I00 in such manner that the alternatingmagnetic flux set up by it will pass through the disc I00, and theopposed windings 00 and 01 are arranged side by side on the oppositeside of the disc in such positions relative to the winding IOI that whenthe disc I00 is stationary equal numbers of lines of the alternatingmagnetic flux set up by winding IIII will pass through them. Thus, equaland opposite alternating voltages will be induced in the windings 00 and01 with the result that normally the resultant damping voltage will bezero. When the disc I00 is rotated, however, the alternating magneticflux set up by the winding IN is distorted, and depending upon thedirection of rotation of the disc, more lines of flux will pass throughone ing in the appearance of an alternating voltage across the terminalsof these windings.

This induced voltage will be substantially in phase with the linevoltage or displaced 180 therefrom depending upon the direction ofrotation of the disc I00, and as will be apparent, the amplitude of theinduced voltage will be directly dependent upon the speed of rotation ofthe disc. That is, if the speed of rotation of the disc is small, thedegree of distortion of the alternating magnetic field set up by thewinding III is correspondingly small, and as a result the voltageinduced in the windings 06 and 01 will be nearly equal so that theirresultant voltage is opposed winding 00 or 01 than the other, result-,

small. As the speed of rotation oi the disc becomes greater, however,the degree of distortion of the magnetic field will become greater, andthereby the voltage induced in one or the other of the windings 00 or 01will become greater to a corresponding extent than the voltage inducedin the other winding.

In accordance with the present invention the tendency oi vibration andshock to render the apparatus unstable and erratic in operation has beenavoided by providing a supporting structure for the galvanometer movablecoil 1 and the pick-up coil 0 which absorbs to a considerable extentsuch vibration and shock. and also by providing an arrangement fordelaying the enersization of the reversible electrical motor II inresponse to deflection of the pick-up coil 0 for a suitable timeinterval whereby the motor operation is rendered substantiallyindependent of transient deflections of the pick-up coil 0.

Specifically, the galvanometer including the movable coil 1 and thefield structure I0 and pick-up coil 0 are immersed in a suitableelectrically non-conductive liquid such, for example, as oil containedwithin a container I02. The movable coils l and '0 are suspended betweenfixed supports I03 and I04 of insulating material which are mounted inany convenient manner within the container I02 by suitable suspensionsI05 and I06 which are illustrated in detail in Figs. 2-4. In addition, afloat I01 rigid with the coils I and 0 is provided between the latter.The float I01 is of such density that the rigid unit comprised of thecoils I and 0 and the float III is of approximately the same averagedensity as th liquid contained within the container I02. With thisarrangement it will be readil recognized that the susceptibility of thegalvanometer and pick-up coil structure to vibration and shock will beappreciably reduced.

The suspensions I05 and I 00 may be exactly alike, and as shown in Figs.2-4, comprise two thin metallic and ribbon-like conductors I00 and I09which are insulated from each other and are fastened side by side in anyconvenient manner to a strip of Cellophane IIO. One end of thesuspension I05 is suitably fastened to the galvanometer coil I and theother end is connected to the support I03. Similarly one end oi thesuspension I05 is suitably fastened to the pick-up coil 9 and the otherend is connected to the support I04. The ribbon-like conductors of thesuspension I05 conduct the unbalanced potentiometric currents to thegalvanometer coil I, and the corresponding conductors of the suspensionI06 conduct the alternating currents derived in the pick-up coil 8 tothe conductors I6 and I1.

The means for connecting the suspensions I00 and I06 to the supports I03and I04, respectively, comprise a pair of hooks III and III and a partIll of insulating material to which the hooks III and I II are rigidlyfastened on one side as shown. An opening I I4 is provided in the partII3 through which the ribbon-like conductors I08 and I09 are passed fromthe other side of the part III, and the conductors I00 and I0! aresoldered or otherwise connected to the hooks III and H2, respectively.It is noted the electrical circuits for the coils I and 9 are completedthrough the hooks III and III. This arrangement for suspending the coilsI and I is characterized in that it appreciably simplifies theconstruction of the apparatus and in addition reduces to a minimum thenumber of ad- Justments required.

The arrangement referred to hereinbefore for delaying the energizationof the reversible electrical motor I in response to deflection of thepick-up coil 9 to thereby render the operation of the motor I5substantially independent of transient deflections of the pick-up coil 9includes the resistance I8 of lamp 80 and the condenser I9 which areconnected in the input circuits of the valves 99 and 49. In addition, asillustrated, the transformer secondary winding 98 is connected byconductors H5 and H6 to the input terminals of a full wave rectifier IIIwhich may desirably be of the copper oxide type, and the outputterminals of the rectifier III are connected through a resistance IIBacross the resistance I8 and condenser I9. The rectifier III is soconnected in the circuit that when an alternating voltage is induced inthe transformer secondary-winding 88, a direct current potential of thepolarity indicated in Fig. I is produced across the condenser "I9.

In accordance with the present invention the biasing resistance I1 is sochosen as to bias negatively the control grids II and I5 of theelectronic valves 39 and 40 to an extent greater than that required formaximum power output from the amplifier I. Part of the amplifier outputis fed from the transformer secondary winding 88 through the rectifierIII to the resistance I8 to thereby produce a direct current potentialacross the latter of the proper polarity to oppose the biasing potentialacross the resistance Thus, as the power output from the amplifier Igradually increases from some small value, the negative bias on thecontrol electrodes 'II and 15 is gradually decreased, and as 'aconsequence, the power output from the amplifier I then increasesrapidly as illustrated by curve A in Fig.5. In Fig. 5 the horizontalaxis indicates the degree of deflection of the pick-up coil 9 from theposition of zero inductive relation with the alternating field set up bythe field structure Ill, and the vertical axis indicates the poweroutput from the amplifier I.

In Fig. 5 curve 13 illustrates the general form of the relation betweenthe extent of deflection of the coil 9, or in effect the input voltageto the amplifier I, and the power output from the amplifier which isobtained when the deflection and time delay provisions includingelements 88, III, I8 and I9 are not employed. On curve B the point Frepresents the amplifier power output which is necessary to actuate thereversible motor I5 for rotation. The additional power output obtainablerepresents reserve to overcome excessive friction of the motor shaft,contact I4 along resistances I3, and pen 20 along chart 2|, etc.

It will be apparent to those skilled in the art that curve A representsa more desirable relation than that shown by curve B since almost twiceas much deflection of the pick-up coil 9 is reouired to produce the sameoutput from the amplifier I as represented by the point F while nogreater deflection of the pick-up coil 9 is required for maximum outputfrom the amplifier than in curve B.

Curve C represents a still more desirable relation than curve B. Curve Cindicates small power output from the amplifier I for very sudden orpractically instantaneous deflections of the pickup coil 9 which may becaused by vibration or shock not eliminated by the immersion of thegalvanometer structure in the liquid in container I02. Curves D, E and Ashow the increased output from the amplifier I for slower deflections ofthe pick-up coil 9 requiring the times T=0.25 second, T=0.50 second, andT=1 second to infinity to reach the value for maximum torque. Thus, forsudden deflections of the pick-up coil 9 due to shock or vibration, thepower output obtainable from the amplifier will not be sumcient toenergize the motor I5 to produce motion of. the contact I4 and pen 20.It will be understood that the times or values of T indicated are merelyillustrative and that these or other values may be found most desirableto employ in practical embodiments of the invention-depending upon thedesign.

Curve A, therefore, illustrates the "deflection delay characteristic andcurves C, D and E illustrate the time delay characteristic. These twocharacteristics are obtained simultaneously by means of the circuitarrangement shown in Fig. 1 and described above and including theelements 88, I", I8, and I9.

It is noted thatwhen the resistance I9 is o the type which has anappreciable temperature coeflicient of resistance, that is increases inresistance several times, for example,. fiveor six times in a second ortwo when heated,.a time delay characteristic as shown in curves C, D andE may be obtained. Condenser I9 is utilized to filter the output of therectifier III and may also be so chosen as to increase the time lag ofthe resistance 18.

This arrangement provides a simple and efiicient means for obtainingdeflection-and time delay, and is operative to greatly reduce theefiects of shocks and vibration upon the operation of the apparatus.

It will be apparent that the reversible electrical motor I5 may beemployed to operate a valve II9 positioned in a fuel supply pipe I29 tothe furnace 2 for varying the supply of heating agent to the furnace 2,or preferably a separate reversible electrical motor may be so employed.For example, asillustrated in the drawing a reversible electrical motorI2I having two opposed field windings (not shown) may be used for thispurpose. The reversible motor I2I is mechanically connected in anysuitable manner to the valve H9 and is adapted to adjust the latter toits open or closed position depending upon the direction to which themotor I2I is energized for rotation. The mechanical connection of themotor I2I to the valve H9 is such as to increase and decrease the supplyof heating agent to the furnace 2 as the furnace temperature falls belowor rises above a predetermined level.

The motor I2I is energized for rotation in one direction or the otherdepending upon which of the two opposed field windings is energized bymeans of a switch I22. As illustrated in Fig. 1 current flows from thesupply line L through a conductor I23 to a switch arm I24 which isinsulated from but may be carried by the carriage I9 which carries thepotentiometric slidewire contact I4 and the pen 20, thence by either oftwo spaced contacts I25 or I26, conductors I2I or I28, and one field orthe other field of the motor I2I to the supply line L Although not shownthe contacts I25 and I26 of the switch I22 are made adjustable so thatboth the control point setting and sensitivity of the apparatus may beset in a manner well known in the art.

While in accordance with the provisions of the statutes, I haveillustrated and described the best form of my invention now known to me,it will be apparent to those skilled in the art that changes may be madein the form of the apparatus disclosed without departing from the spiritof my invention as set forth in the appended claims, and that certainfeatures of my invention may sometimes be used to advantage without acorresponding use of other features.

Having now described my invention, what I claim as new and desire tosecure by Letters Pa cut, is:

1. In combination, a primary deflecting ele l ment responsive to avariable condition, to establish an alternating fleld including anelement adapted tobe connected to a source of alternating current, apick-up coil disposed in said fleld,

a mechanical connection between said primary is deflecting element andsaid pick-up coil whereby the latter is rotated to zero inducdveposition in said alternating fleld or in either direction therefrom tothereby cause the induction of an alternating current of one phase or of'20 opposite phase in said pick-up coil accordingly as said conditionvaries, a container including a liquid in which said primary deflectingelement and pick-up coil are immersed, said liquid tending to absorbshock and vibration to which said primary deflecting element and pick-upcoil would otherwise be subjected, a secondary element mechanicallyseparate from said primary deflecting element and adapted to bedeflected in one sense or in mother sense under control of said primary'30 deflecting element, and phase responsive means controlled by saidpick-up coil to deflect said secondary element said phas'e responsivemeans including means to render the operation of said secondary elementsubstantially independent of both transient deflections of saidgalvanometer and small, gradual deflections thereof.

2. in combination, a primary deflecting element responsive to a variablecondition, means to establish an alternating fleld including an elementadapted to be connected to a source of alternating current, a pick-upcoil disposed in said fleld, a mechanical connection between saidprimary deflecting element and said pick-up coil whereby the latter isrotated to zero inductive position in said alternating fleld or ineither di rection therefrom to thereby cause the induction of analternating current of one phase or of opposite phase in said pick-upcoil accordingly as said condition varies, a container including a liq-'50 uid in which said primary deflecting element and pick-up coil areimmersed, said liquid tending to absorb shock and vibration to whichsaid primary deflecting element and pick-up coil would otherwise besubjected, a float rigid with said primary deflecting element and saidpick-up coil and also immersed within said liquid, said float having adensity such that the average density of said primary deflectingelement, said pick-up coil and said float is approximately the same as00 said liquid, a secondary element mechanically separate from saidprimary deflecting element and adapted to be deflected in one sense orin another sense under control of said primary deflecting element, andphase responsive means controlled as by said pick-up coil to deflectsaid secondary element said phase responsive means including means torender the operation of said secondary element substantially independentof both transient deflections of saidgalvanometer and small, 10 gradualdeflections thereof.

3. Measuring apparatus including a self balancing electrical network,means responsive to the variations in. a condition under measurement tounbalance said network, a device to rebai- 79 ance said network, andmeans to control the operation of said device including a primarydeflecting, element responsive to the state of balance of said network,means to establish an alternating fleld including an element adapted tobe connected to a source of alternating current, a pick-up coil disposedin said fleld, a mechanical connection between said primary deflectingelement and said pick-up coil whereby the latter is rotated to zeroinductive position in said alternating field or in either directiontherefrom to thereby cause the induction of an alternating current ofone phase or of opposite phase in said pick-up coil accordingly as saidcondition varies, a container including a liquid in which said primarydeflecting element and pick-up coil are immersed, said liquid tending toabsorb shock and vibration to which said primary deflecting elementwould otherwise be subjected, a float rigid with said primary deflectingelement and said pick-up coil and also immersed within said liquid, saidfloat having a density such that the average density of said primarydeflecting element, said pick-up coil and said float is approximatelythe same as said liquid, and phase responsive means controlled by saidpick-up coil to actuate said device said phase responsive meansincluding means to render the operation of said device substantiallyindependent of both transient deflections of said galvanometer andsmall, gradual deflections thereof.

4. Measuring apparatus including a self balancing electrical network,means responsive to the variations in a condition under measurement tounbalance said network, a device to rebalance said network, a reversibleelectrical motor to actuate said device, and means to control theoperation of said device including a primary deflecting elementresponsive to the state of balance of said network,.means to establishan alternating fleld including an element adapted to be connected to asource of alternating current, a pick-up coil disposed in said field, amechanical connection between said primary deflecting element and saidpick-up coil whereby the latter is rotated to zero inductive position insaid alternating fleld or in either direction therefrom to thereby causethe induction of an alternating current of one phase or of oppositephase in said pick-up coil accordingly as said condition varies, acontainer including a liquid in which said primary deflecting elementand pick-up coil are immersed, said liquid tending to absorb shock andvibration to which said primary deflecting element would otherwise besubjected, a float rigid with said primary deflecting element and saidpick-up coil and also immersed within said liquid, said float having adensity such that the average density of said primary deflectingelement, said pick-up coil and said float is approximately the same assaid liquid, and phase responsive means controlled by said pick-up coilto control the energization of said reversible elec trical motor saidphase responsive means including means to render the operation of saidmotor substantially independent of both transient deflcctions of saidgalvanometer and small, gradual v deflections thereof.

5. In combination, a primary deflecting element responsive to a variablecondition, means to establish an alternating fleld including an elementadapted to be connected to a source of alternating current, a pick-upcoil disposed in said fleld, a mechanical connection between saidprimary deflecting element and said pick-up coil whereby the latter isrotated to zero inductive postition in said alternating field or ineither direction therefrom to thereby cause the induction of analternating current of one phase or of opposite phase in said pick-upcoil accordingly as said condition varies, a container including aliquid in which said primary deflecting element and pick-up coil areimmersed, said liquid tending to absorb shock and vibration to whichsaid primary deflecting element and pick-up coil would otherwise besubjected, a secondary element mechanically separate from said primarydeflecting element and adapted to be deflected in one sense or inanother sense under control of said primary deflecting element, phaseresponsive means controlled by said pick-up coil to actuate saidsecondary element in said one sense or said another sense depending uponthe phase of the alternating current induced in said pickup coil, andmeans responsive to deflections of said pick-up coil to control theoperation of said last mentioned means to render the operation of saidsecondary element substantially independent of transient deflections ofsaid primary deflecting element and pick-up coil.

6. Measuring apparatus including a self balancing electrical network,means responsive to the variations in a condition under measurement tounbalance said network, a device to rebalance said network, a reversibleelectrical motor to actuate said device, and means to control theoperation of said device including a primary deflecting elementresponsive to the state of balance of said network, means to establishan alternating fleld including an element adapted to be connected to asource of alternating current, a pick-up coil disposed in said field, amechanical connection between said primary deflecting element and saidpick-up coil whereby the latter is related to zero inductive position insaid alternating fleld or in either direction therefrom to thereby causethe induction of an alternating current of one phase or of oppositephase in said pick-up coil accordingly as said condition varies, acontainer including a liquid in which said primary deflecting elementand pick-up coil are immersed, said liquid tending to absorb shock andvibration to which said primary deflecting element would otherwise besubjected, a float rigid with said primary deflecting element and saidpick-up coil and also immersed within said liquid, said float having adensity such that the average density of said primary deflectingelement. said pick-up coil and said float is approximately the same assaid liquid, phase responsive means controlled by said pick-up coil tocontrol the energization of said reversible electrical motor, and meansresponsive to deflections of said pick-up coil to control the operationof said phase responsive means to render the operation of saidreversible electrical motor substantially independent of transientdeflections of said primary deflecting element and pick-up coil.

7. Measuring apparatus including a self balancing electrical network,means responsive to the variations in a condition under measurement tounbalance said network, a device to rebalance said network, a reversibleelectrical motor to actuate said device, and means to control theoperation of said device including a primary deflecting elementresponsive to the state of balance of said network, means to establishan alternating fleld including an element adapted to be connected to asource of alternating current, a pick-up coil disposed in said field, amechanical connection between said primary deflecting element and saidpick-up coil whereby the latter is related to zero inductive position insaid alternating fleld or in either direction therefrom to thereby causethe induction of an alternating current of one phase or of oppositephase in said pick-up coil accordingly as said condition varies, acontainer including a liquid in which said primary deflecting elementand pick-up coil are immersed, said liquid tending to absorb shock andvibration to which said primary deflecting element would otherwise besubjected, a float rigid with said primary deflecting element and saidpick-up coil and also immersed within said liquid, said float having adensity such that the average density of said primary deflectingelement, said pick-up coil and said float is approximately the same assaid liquid, electronic means having an amplifying stage and a motordriving stage, a connection between said pick-up coil and the inputcircuit of said amplifying stage, a connection between the outputcircuit of said amplifying stage and the input circuit of said motordriving stage, a connection between the output circuit of said motordriving stage and said reversible electrical motor, means to bias theinput circuit of said motor driving stage in such a manner as to tend tomaintain the output current from said motor driving stage insuflicientto actuate said motor for rotation, and delayed operating means to feedback at least part of the current from the output circuit of said motordriving stage to the input circuit thereof to neutralize the effect ofsaid biasing means.

8. The combination of claim '7 wherein said delayed operating meanscomprises a rectifier, a connection from the (mtput circuit of saidamplifier to the input circuit of said rectifier, a resistance connectedto the output circuit of said rectifier and also connected in theinput'circuit of said motor driving stage, said resistance having anappreciable temperature coefficient of resistance, and a condenserconnected across said resistance.

9. In combination, a primary deflecting element responsive to a variablecondition, a container including a liquid in which said primarydeflecting element is immersed, said liquid tending to absorb shock andvibration to which said primary deflecting element otherwise would besubjected, a phase responsive secondary element mechanically separatefrom said primary deflecting element and adapted to be actuated undercontrol of said primary deflecting element. means to translate thedeflections of said primary deflecting element from a predeterminedposition into an alternating current of one phase or of opposite phase,electronic amplifying means having a plurality of stages and having aninput circuit to which said alternating current is impressed and anoutput circuit controlled by said input circuit, a connection betweenthe output circuit of said electronic amplifying means and said phaseresponsive secondary element, means to bias the input circuit of one ofthe stages of said amplifying means tending to maintain the outputcurrent from said amplifier insufficient to actuate said phaseresponsive secondary element, and delayed operating means to feed backat least part of the current from the output circuit of said electronicamplifying means to the input circuit of said one stage to neutralizethe effect of said biasing means.

10. In combination, a primary deflecting element responsive to avariable condition, a container including a liquid in which said primarydeflecting element is immersed, said liquid tending to absorb shock andvibration to which said primary deflecting element otherwise would besubjected, a secondary element mechanically separate from said primarydeflecting element and adapted to be deflected under control of saidprimary deflecting element, means to translate the deflections of saidprimary deflecting element into a fluctuating current, electronicamplifying means having an input circuit to which said fluctuatingcurrent is impressed and an output circuit controlled by said inputcircuit, a connection between the output circuit of said electronicamplifying means and said secondary element, means to bias the inputcircuit of said electronic amplifying means tending to maintain theoutput current from said amplifler insufficient to actuate saidsecondary element, and delayed operating means to feed back at leastpart of the current from the output circuit of said electronicamplifying means to the input circuit thereof to neutralize the effectof said biasing means.

11. The combination of claim 10 wherein said delayed operating meanscomprise a rectifier, a connection from the output circuit of saidamplifler to the input circuit of said rectifier, a resistance connectedto the output circuit of said rectifier and also connected in the inputcircuit of said electronic amplifying means, said resistance having anappreciable temperature coefficient of resistance, and a condenserconnected across said resistance.

12. In combination, a primary deflecting element responsivetto avariable condition, a secondary element mechan cally separate from saidprimary deflecting element and adapted to be deflected under control ofprimary deflecting element, means to translate the deflections of saidprimary deflecting element from a predetermined position into afluctuating current, electronic amplifying means having an input circuitto which said fluctuating current is impressed and an output circuitcontrolled by said input circuit, a connection between the outputcircuit of said electronic amplifying means and said secondary element,means to bias the input circuit of said electronic amplifying meanstending to maintain the output current from said amplifler insufficientto actuate said secondary element, and delayed operating means to feedback at least part of the current from the output circuit of saidelectronic amplifying means to the input circuit to neutralize theeffect of said biasin means.

13. The combination of claim 12 wherein said delayed operating meanscomprise a rectifler, a connection from the output circuit of saidamplifler to the input circuit of said rectifier, and a resistancehaving a appreciable temperature coeflicient of resistance connected tothe output circuit of said rectifler and also connected in the inputcircuit of said electronic amplifying means.

14. Measuring apparatus including a self balancing electrical network,means responsive to the variations in a condition under measurement tounbalance said network, a device to rebaiance said network, a reversibleelectrical mtor to actuate said device, and means to control theoperation of said motor including a primary deflecting elementresponsive to the state of balance of said network, means to translatethe dc flections of said primary deflecting element from a predeterminedposition into an alternatinl current of one phase or of opposite phase,electronic amplifying means having an input circuit and an outputcircuit, means to apply said alternating voltage to the input circuit ofsaid elsetronic amplifying means, a connection between the outputcircuit of said electronic amplifying means and said reversibleelectrical motor, means to bias the input circuit of said electronicamplifying means in such manner as to tend to maintain the out putcurrent from said electronic amplifying means insufficient to actuatesaid motor for rotation, and delayed operating means to feed back atleast part of the current from the output circuit of said electronicamplifying'means to the input circuit thereof to neutralize the effectof said biasing means.

15. Measuring apparatus including a self balancing electrical network,means responsive to the variations in a condition under measurement tounbalance said network, a device to rebalance said network, a reversibleelectrical motor to actuate said device, and means to control theoperation of said motor including a primary deflecting elementresponsive to the state of balance of said network, means to establishan alternating field including an element adapted to be connected to asource of alternating current, a pick-up coil disposed in said field, amechanical connection between said primary deflecting element and saidpick-up coil whereby the latter is rotated to zero inductive position insaid alternating field or in either direction therefrom to thereby causethe induction of an alternating current of one phase or of oppositephase in said pick-up coil accordingly as said condition varies,electronic amplifying means having an amplifying stage and a motordriving stage, a connection between said pick-up coil and the inputcircuit of said amplifying stage, a connection from the output circuitof said amplifying stage and the input circuit of said motor drivingstage, a connection between the output circuit of said motor drivingstage and said reversible electrical motor, means to bias the inputcircuit of said motor driving stage in such a manner as to tend tomaintain the output current from said motor driving stage insufficientto actuate said motor for rotation, and delayed operating means to feedback at least part of the current from the output circuit of said motordriving stage to the input circuit thereof to neutralize the effect ofsaid biasing means.

16. The combination of claim 15 wherein said delayed operating meanscomprises a rectifier, a connection from the output circuit of saidmotor driving stage to the input circuit of said rectifier, a resistanceconnected to the output circuit of said rectifier and also connected inthe input circuit of said motor driving stage, said resistance having anappreciable temperature coefiicient of resistance, and a condenserconnected across said resistance.

1'7. In combination, a primary deflecting element responsive to avariable condition, a secondary element adapted to be deflected undercontrol of said primary deflecting element, electronic amplifying meanshaving an input circuit controlled by said primary deflecting elementand an output circuit controlled by said input circuit, a connectionbetween the output circuit of said electronic amplifying means and saidsecondary element, means to bias the input circuit of said electronicamplifying means tending to maintain the output current from saidamplifying means insuflicient to actuate said secondary element, anddelayed operating means to feed back at least a part of the current fromthe output circuit of said electronic amplifying means to the inputcircuit to neutralize the etfect of said biasing means.

18. In combination, a galvanometer responsive to a variable condition,an exhibiting element mechanically separate from said galvanometer andadapted to be actuated under control of said galvanometer, meanscontrolled by said galvanometer to actuate said exhibitin element, andmeans controlled by said galvanometer to control the operation of saidlast mentioned means to render the operation of said exhibiting elementsubstantially independent of both transient deflections of saidgalvanometer and small, gradual deflections thereof.

19. In combination, a galvanometer having a movable elementwhichdeflects in accordance with the variations in a variable condition,a container including a liquid in which said galvanometer is immersed,said liquid tending to absorb shock and vibration to which saidgalvanometer would otherwise be subjected, a float eter movable elementand said float and the density of said liquid, an exhibiting elementmechan-ically separate from said galvanometer and adapted to bedeflected under control of said gaivanometer, means controlled by saidgalvanomcter to deflect said exhibiting element, and means controlled bysaid galvanometer to control the operation of said last mentioned meansto render the operation of said exhibiting element substantiallyindependent of both transient deflections of said galvanometer andsmall, gradual deflections thereof.

20. In combination, a galvanometer having an element deflecting inresponse to variations in a variable condition, a container including aliquid in which said galvanometer is immersed, said liquid tending toabsorb shock and vibration to which said galvanometer otherwise would besubjected, an exhibiting element mechanically separate from saidgalvanometer and adapted to be deflected under control of saidgalvanometer. means controlled by said galvanometer to deflect saidexhibiting element, and means controlled by said galvanometer to controlthe operation of said last mentioned means to render the operation ofsaid exhibiting element substantially independent of both transientdeflections of said galvanometer and also small, gradual deflectionsthereof.

21. In combination, a primary deflecting element responsive to avariable condition, means to establish an alternating field including anelement adapted to be connected to a source of alternating current, apick-up coil disposed in said fleld, a mechanical connection betweensaid primary deflecting element and said pick-up coil whereby the latteris rotated to zero inductive position in said alternating field or ineither direction therefrom to thereby cause the induction of analternating current of one phase or of opposite phase in said pick-upcoil accordingly as said condition varies, a secondary elementmechanically separate from said primary deflecting element and adaptedto be deflected in one sense or in another sense under control of saidprimary deflecting element, phase responsive means controlled by saidpick-up coil to actuate said secondary element in said one sense or saidanother sense depending upon the phase of the alternating currentinduced in said pick-up coil, and means responsive to deflections ofsaid pickup coil to control the operation of said last mentioned meansto render the operation of the secondary element substantiallyindependent of transient deflections of said primary deflecting elementand pick-up coil,

22. Measuring apparatus including a self balancing electrical network,means responsive to the variations in a condition under measurement tounbalance said network, a device to rebalance said network, a reversibleelectrical motor to actuate said device, and means to control theoperation of said device including a primary deflec'ting elementresponsive to the state of balance of said network, means to establishan alternating field including an element adapted to be connected to asource of alternating current, a pick-up coil disposed in said field, amechanical connection between said primary deflecting element and saidpick-up coil whereby the latter is related to zero inductive position insaid alternating field or in either direction therefrom to thereby causethe induction of an alternating current of one phase or of oppositephase in said pick-up coil accordingly as said condition varies, phaseresponsive means controlled by said pickup coil to control theenergization of said reversible electrical motor, and means responsiveto deflections of said pick-up coil to control the operation of saidphase responsive means to rem der the operation of said reversibleelectrical motor substantially independent of transient deflections ofsaid primary deflecting element and pick-up coil.

HARRY S. JONES.

